Goldak 902 Operating Manual
CONTENTS PAGE NO.
A. General Description . . . . . . . . . . . . . . . . . . . . . . . .1
B. Major Components And Accessories . . . . . . . . . .1
1. Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2. Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3. Direct-Connection Cable (DCC) . . . . . . . . . . . . . .5
4. Ground Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
5. GC-2 Cable Clamp . . . . . . . . . . . . . . . . . . . . . . .5
6. Headphones . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
7. Carrying Bag . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
C. Modes Of Operation . . . . . . . . . . . . . . . . . . . . . . . .6
D. Operating Procedures . . . . . . . . . . . . . . . . . . . . . . .7
1. Energizing a Line to be Traced . . . . . . . . . . . . . .7
a) Inductive Energizing . . . . . . . . . . . . . . . . . . . .7
b) Conductive Energizing . . . . . . . . . . . . . . . . . . .9
2. Tracing an Energized Line . . . . . . . . . . . . . . . . .11
a) Peak Detection Method . . . . . . . . . . . . . . . . .11
b) Null Detection Method . . . . . . . . . . . . . . . . . .14
c) Determining Depth of a Line . . . . . . . . . . . . . .15
3. Finding Lines of Completely
Unknown Location . . . . . . . . . . . . . . . . . . . . . . .17
4. Locating Hidden Valve Caps
and Manholes . . . . . . . . . . . . . . . . . . . . . . . . . . .18
E. Miscellaneous Notes and Suggestions . . . . . . . .20
F. Instrument Maintenance . . . . . . . . . . . . . . . . . . . .20
1. Battery Replacement . . . . . . . . . . . . . . . . . . . . .20
2. Mechanical Care . . . . . . . . . . . . . . . . . . . . . . . . .21
3. Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . .22
G. Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
A. General Description:
The Goldak Model 902 is a hand-held electronic pipe and cable
locator, designed according to the classic “split-box” concept. Like
its predecessors in the Model TR series, the Model 902 is used to
trace underground conductive networks such as water and gas
mains, telephone, cable TV and electric power cables, and any continuously conductive pipe or cable. Also, as with traditional “splitbox” locators, the Model 902 may be used to electronically determine the depth of buried lines, by employing simple operating techniques.
However, the Model 902 also incorporates features that are not
found in traditional locators. Designed with patented SI (super-inductive) technology, the Model 902 packs superior performance into a
convenient, hand-held package that is significantly smaller than
other two-box locators. Durability of the Model 902 is insured by
solid construction in a tough, Xenoy housing. Also, to enhance locating convenience, sub-surface metallic structures, including valve
caps, risers and manhole covers, can be found easily during tracing
by pressing a single push-button switch.
B. Major Components and Accessories:
1. Transmitter.
The transmitter generates a signal which is to be used to
“energize” the conductive line to be located. When a line is
energized, it radiates the generated signal in a pattern which
corresponds to the direction of the line, and which may be used
not only to trace the line but also to determine its depth. The
signal may be transferred to the line by one of two methods:
inductively or conductively. Inductive transferrance does not
require the line to be electrically exposed. Conductive transferrance requires that the transmitter be connected physically via
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cable to the line to be traced. Section D of this manual,
“Operating Procedures,” explains these transmission methods in greater detail. A detailed explanation of the transmitter
features and controls follows here (refer to Fig. 1):
a) The POWER Switch. This booted push-button switch
controls the power state of the transmitter. Depressing
this switch so that the adjacent “BATT” light illuminates
“turns on” the transmitter, causing it to generate a signal.
Depressing the switch again will deactivate the transmitter.
b) The BATT Indicator. This LED is lit when the transmitter is
activated and the condition of the battery source is good.
If this LED does not illuminate when the POWER switch is
pressed, or it becomes unlit during operation, the batteries need to be replaced.
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c) The PULSE Switch. This switch controls whether the
signal generated by the transmitter is continuous or
pulsed at a frequency of 5 to 10 times per second.
Pulsing the signal allows it to be easily identified and also
conserves the transmitter's batteries. The transmitter is in
“pulse mode” when the BATT indicator is flashing.
d) The OUTPUT LEVEL Switch. This push-button controls
the intensity of the signal that is generated by the transmitter. Depressing this button so that the “HI” indicator is
lit transmits the maximum amount of signal for any given
signal transfer method. When the “HI” indicator is unlit,
the signal output is reduced.
e) The HI Indicator. As explained above, this LED indicates
the level of signal that is presently being transmitted.
f) The DIRECT OUTPUT Jack. Inserting the plug of the
directconnection cable (hereafter referred to as the
“DCC”) into this jack switches the transmitter into “conductive” mode. In this mode, a line may be energized
directly by physically connecting the red clip of the DCC
to an exposed part of the line.
2. Receiver.
The receiver is used to detect the signal generated by the
transmitter, and therefore to trace the conductive line that the
transmitter is energizing. While locating a line, the operator
may use the receiver in either of two tracing modes: peak
and null. When using peak mode, the operator searches for
a maximum signal; this is the most sensitive mode. In null
mode, the operator looks for places where the signal vanishes. A single pushbutton sets the receiver in an auxiliary
detection mode (locate mass) which allows the operator to
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conveniently find buried metallic masses, such as valve caps
or manhole covers. Section D of this manual, “Operating
Procedures,” contains more details about these locating
methods and others. Specific features and controls found on
the 902 receiver panel are described here (refer to Fig. 2):
a) The POWER Switch. This push-button switch activates
and deactivates the receiver. The receiver is activated
(“on”) when the POWER switch is depressed so that the
“BATT” light above this switch illuminates. Depressing the
switch again will turn the receiver “off”.
b) The BATT Indicator. When the condition of the batteries in
the receiver is good, this LED shines when the receiver is
activated. If this indicator does not shine when the
POWER switch is pressed, or it stops shining during
operation, then the batteries need to be replaced.
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c) The SENSITIVITY Switch. Using this button will toggle the
sensitivity of the receiver between a low and a high state.
That is, this switch controls the receiver’s overall sensitivity to the signal produced by the 902 transmitter. The LED
indicator above this switch monitors what the present
sensitivity mode of the receiver is. (NOTE: This switch
does NOT control the sensitivity of the receiver while in
“locate mass” mode.)
d) The HI Indicator. This LED indicates the present sensitivity
of the 902 receiver when in normal tracing mode. The
indicator will be lit to correspond to a state of high sensitivity. Likewise, the LED will be darkened in the low
sensitivity mode.
e) The LOCATE MASS Switch and Indicator. Pressing this
switch so that the LED indicator directly above it illuminates changes the 902 receiver from a line tracer to a
metallic mass locator. Examples of buried masses that the
receiver is able to find in this mode are valve caps and
manhole covers. Using the instrument in this mode
disables normal receiving functions.
f) The SIGNAL LEVEL Control. This knob is the most impor-
tant control on the 902 receiver from an operating standpoint. While in tracing mode, use this knob to gradually
adjust the sensitivity of the receiver to the transmitted
signal. When tracing in “peak” mode, use this control to
set the point of maximum signal on the response meter;
in “null” mode, use it to adjust the width of the signal null.
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g) The Light Bar Meter. This solid-state LED bar meter pro-
vides a visual indication of the level of signal presently
being received. As described above, the response meter
will indicate both peaks and vanishing points in the signal
surrounding the line being traced.
h) Speaker. A water-resistant, small but powerful mylar
speaker delivers a strong audio output corresponding to
the signal received by the 902. In tracing mode, the sound
will track the LED meter response; however, in masslocating mode, the speaker delivers a continuous tone,
the frequency of which will rise when the receiver is
brought near to a metallic mass.
i) Headphones Jack. All sound normally supplied by the
speaker will be channelled to headphones when the
headphone plug is inserted here.
j) 45° Level Guage. When making a determination of line
depth, the operator will often find this small level helpful.
Oriented at a 45° angle with respect to the antenna, the
bubble in the level will center itself when the antenna is
positioned at 45° compared to level ground. See section
D of this manual for more information on determining line
depth.
3. Direct-Connection Cable (DCC).
Included with every Model 902 instrument, this accessory
consists of a phone jack wired to two separate copper
clamps. Use this cable to inject the transmitter signal directly
into a specific line, thus conductively energizing it. To
accomplish this, connect the red clamp to the exposed line,
and optionally attach the black lead to some ground if
increased tracing distance is desired.
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4. Ground Rod.
This U-shaped rod, also included with every 902, simply
gives the operator a means of establishing a solid ground for
conductive tracing. To use the ground rod, push it into some
soil, and clip the black lead of the DCC to it.
5. GC-2 Cable Clamp.
This accessory is useful when the operator wishes to energize a specific line, but there is no electrically exposed area
to make a conductive hook up. If the GC-2 is clamped
around a specific line, it will inductively energize the line with
a focused signal. The line will become considerably more
energized than surrounding lines, and therefore easily traceable. The Model GC-2 clamp is sold separately.
6. Headphones are also sold separately from the Model 902.
Any set of headphones may be used with the Model 902
Locator, provided it has a standard quarter-inch plug. We
recommend a comfortable “walkman” style of headphones,
which comes with a quarter-inch plug adapter.
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7. Carrying Bag.
There are two kinds of carrying bag available for the 902
locator, both constructed from rugged nylon canvas. The
smaller bag comes with the instrument originally and contains only enough room to carry the instrument and its basic
set of accessories. The larger bag has additional pouches
specifically tailored to house the GC-2 cable clamp, a set of
headphones, and other miscellaneous items. The larger bag
is sold separately.
C. Modes of Operation:
1. Transmission Modes.
There are two modes of signal transmission for the Model
902 Pipe and Cable Locator: inductive and conductive. Two
discrete output levels may be selected for either mode, and
the operator may choose to pulse the signal in either mode
of transmission for easier identification.
a) Inductive Transmission. In inductive mode, the 902 trans-
mitter produces a radio signal capable of penetrating air,
ground, and other media in order to energize a nearby
conductive line. Having been effected by the transmitted
signal, the line then conducts the signal along its path.
The signal pattern surrounding the line corresponds to the
path of the line itself. Therefore, the operator may use the
902 receiver to trace the direction of the line and to
determine its depth from the signal pattern surrounding it.
Although energizing a line inductively can be convenient
and sometimes necessary, this method typically is less
precise than conductive transmission in its ability to
isolate a desired line.
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b) Conductive Transmission. To activate this mode of trans-
mission, the operator inserts the plug of the direct-connection cable into the DIRECT OUTPUT jack on the transmitter control panel. Connecting the clip of the DCC
directly to some exposed part of the line will channel the
radio signal into the line through the cable. The line then
conducts the signal exactly as it does if it is inductively
energized, and the receiver can trace the line the same
as well. However, in this mode, energizing is much more
precise as well as more efficient. Therefore, one can generally expect longer and more reliable traces when using
conductive transmission. This is the preferred method of
transmission, and should be used in most cases when a
portion of the line to be traced is exposed.
2. Receiving Modes.
As for the transmitter, there are two general modes of location for the 902 receiver: line tracing and mass locating.
For line tracing, the operator may choose between two
discrete levels of receiver sensitivity.
a) Line Tracing. This mode is used exclusively to detect the
signal generated by the 902 transmitter, and therefore to
locate lines which the transmitter is energizing. When
tracing, one may choose to use either of two methods:
peak or null. The operator selects the method solely by
how he positions the receiver with respect to the line
being traced. Peak method is selected by holding the
receiver so that the plane of the face of the receiver is
perpendicular
to the surface above the line being traced.
Holding the receiver so that the face lies parallel
to this
surface causes the signal to vanish when the energized
line is located; this is null method. In line tracing mode,
the operator may ascertain line depth by using simple
techniques.
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